Ultra-high strength petroleum casing and preparation method thereof

Abstract

The invention discloses an ultra-high strength petroleum casing and a preparation method thereof, including the design of steel grade of the casing, tube blank and casing preparation and other aspects. The chemical composition of the casing is as follows by mass percentage: C: 0.23% to 0.30%, Si: 0.45% to 0.65%, Mn: 0.90% to 1.10%, P≤0.012%, S≤0.003%, Cr: 0.50% to 0.70%, Mo: 0.30% to 0.50%, Ni: 0.30% to 0.50%, V: 0.05% to 0.10%, Ti: 0.01% to 0.03%, Re: 0 to 0.003%, Al: 0.010% to 0.015%, Ca: 0.006% to 0.010%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities. The preparation method includes smelting, hot rolling, controlled rolling and controlled cooling, heat treatment and other processes, and the threaded casing products are processed, and the strength levels can reach the requirements of 150, 155, 160, 165, and 170 ksi steel grades respectively, and have good plasticity, toughness and economy. It can meet the needs of ultra-high strength casing for the efficient development of oil and gas in ultra-deep and extra-deep wells under complex working conditions.

Description

Technical Field

[0001] The invention relates to an ultra-high strength casing and a preparation method thereof, in particular to an ultra-high strength petroleum casing and a preparation method thereof.

[0002] Its strength levels meet the requirements of 150, 155, 160, 165 and 170ksi steel grades respectively. It has a reasonable match of high strength, good plasticity and toughness, and good economy. It can meet the needs of ultra-high strength casing for the efficient development of ultra-deep wells and extra-deep wells in complex working conditions. Background Art

[0003] As the oil and gas industry develops in depth, the proportion of deep wells and ultra-deep wells is increasing, and the ultra-deep wells of 10,000 meters have also been developed, which has put forward a huge demand for ultra-high-strength oil casing. In order to ensure the mechanical properties and performance of ultra-high-strength oil casing, it is necessary to optimize its chemical composition and preparation process. For example, in the design of chemical composition, more alloy elements with higher prices and higher contents are usually added, such as 1% to 1.5% of Cr and Mo, and even 0.20% to 0.30% of V and other alloy elements are often added; resulting in a significant increase in production and manufacturing costs. On the other hand, in the usual hot rolling and heat treatment process of the casing, due to the lack of effective preparation technology, the role of the main alloy elements and micro-alloy elements such as Nb, V, and Ti is not fully exerted, resulting in the strengthening and toughening effect of the casing is not ideal. Third, the strength and toughness of steel materials often show a phenomenon of one gain and the other loss. The pursuit of too high toughness often requires sacrificing strength, while the pursuit of high strength and high toughness at the same time will lead to the complexity of alloy design and preparation process, resulting in a significant increase in preparation costs. How to further optimize the composition design of ultra-high strength casing and comprehensively regulate the matching preparation process without significantly increasing the cost of casing alloy design and preparation has become an important topic in the research and development of ultra-high strength casing.

[0004] Therefore, the existing technology needs to be further developed and improved. Summary of the invention

[0005] In view of the above-mentioned deficiencies of the prior art, the present invention proposes an ultra-high strength oil casing using medium-low C, Mn, a small amount of Cr, Mo, Ni, Si, V-Ti-(Re) composite microalloying and a preparation method thereof, aiming to provide an ultra-high strength oil casing that takes into account strength, plasticity, toughness, safety, reliability and economy.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] In a first aspect, an ultra-high strength petroleum casing, wherein the chemical composition of the casing is as follows by mass percentage: C: 0.23% to 0.30%, Si: 0.45% to 0.65%, Mn: 0.90% to 1.10%, P≤0.012%, S≤0.003%, Cr: 0.50% to 0.70%, Mo: 0.30% to 0.50%, Ni: 0.30% to 0.50%, V: 0.05% to 0.10%, Ti: 0.01% to 0.03%, Re: 0 to 0.003%, Al: 0.010% to 0.015%, Ca: 0.006% to 0.010%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

[0008] Optionally, the ultra-high strength petroleum casing, wherein the chemical composition of the casing is as follows by mass percentage: C: 0.23% to 0.24%, Si: 0.45% to 0.49%, Mn: 0.90% to 0.93%, P: 0.010% to 012%, S: 0.001% to 0.002%, Cr: 0.50% to 0.54%, Mo: 0.30% to 0.35%, Ni: 0.30% to 0.34%, V: 0.05% to 0.07%, Ti: 0.01% to 0.03%, Re: 0 to 0.001%, Al: 0.010% to 0.015%, Ca: 0.006% to 0.008%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

[0009] Optionally, the ultra-high strength petroleum casing, wherein the chemical composition of the casing is as follows by mass percentage: C: 0.25% to 0.27%, Si: 0.51% to 0.55%, Mn: 0.94% to 0.96%, P: 0.010% to 012%, S: 0.001% to 0.002%, Cr: 0.55% to 0.58%, Mo: 0.36% to 0.39%, Ni: 0.36% to 0.38%, V: 0.06% to 0.08%, Ti: 0.02% to 0.03%, Re: 0 to 0.001%, Al: 0.012% to 0.013%, Ca: 0.009% to 0.011%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

[0010] Optionally, the ultra-high strength petroleum casing, wherein the chemical composition of the casing is as follows by mass percentage: C: 0.26% to 0.28%, Si: 0.56% to 0.59%, Mn: 0.97% to 1.00%, P: 0.009% to 012%, S: 0.001% to 0.002%, Cr: 0.60% to 0.65%, Mo: 0.41% to 0.45%, Ni: 0.39% to 0.43%, V: 0.07% to 0.08%, Ti: 0.02% to 0.03%, Re: 0 to 0.002%, Al: 0.010% to 0.015%, Ca: 0.012% to 0.015%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

[0011] Optionally, the ultra-high strength petroleum casing, wherein the chemical composition of the casing is as follows by mass percentage: C: 0.27% to 0.29%, Si: 0.58% to 0.60%, Mn: 1.02% to 1.03%, P: 0.010% to 012%, S: 0.001%, Cr: 0.66% to 0.68%, Mo: 0.42% to 0.46%, Ni: 0.44% to 0.46%, V: 0.07% to 0.08%, Ti: 0.02% to 0.03%, Re: 0 to 0.003%, Al: 0.012% to 0.014%, Ca: 0.013% to 0.014%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

[0012] Optionally, the ultra-high strength petroleum casing, wherein the chemical composition of the casing is as follows by mass percentage: C: 0.28% to 0.30%, Si: 0.61% to 0.65%, Mn: 1.05% to 1.10%, P: 0.009% to 010%, S: 0.001%, Cr: 0.64% to 0.70%, Mo: 0.47% to 0.50%, Ni: 0.48% to 0.50%, V: 0.09% to 0.10%, Ti: 0.02% to 0.03%, Re: 0 to 0.003%, Al: 0.013% to 0.014%, Ca: 0.011% to 0.014%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

[0013] In terms of composition design, the present invention adopts medium-low C, adds Mn, adds a small amount of Cr, Mo, Ni, Si, V-Ti-(Re) composite microalloying, adopts Al, Si fully deoxidized killed steel and pure steel technology, and performs Ca treatment on the molten steel. The functions and content ranges of the main elements are as follows:

[0014] C: It is the main strengthening element in steel. Increasing the carbon content can significantly improve the hardenability of steel and thus increase its strength, but too high a carbon content will damage the plasticity and toughness of steel. Taking all factors into consideration, it is advisable to control it within the range of 0.23% to 0.30%.

[0015] Si: Usually used as a permanent element and deoxidizer in steel, it is generally controlled within the range of 0.15% to 0.40%. An appropriate amount of Si can improve the hardenability of steel, thereby improving strength, corrosion resistance and tempering stability, but too high a content will increase the segregation tendency of steel, promote the formation of banded structure, and thus damage the plasticity and toughness of steel. Taking all factors into consideration, it is advisable to control it within the range of 0.45% to 0.65%.

[0016] Mn: Mainly used to improve the hardenability of steel and thus improve strength, it can partially replace the more expensive Cr element, but the Mn element has a greater tendency to segregate, and too high a content will lead to uneven organizational structure and performance. Usually, the Mn content in casing materials with excellent performance is below 1.25%. Taking all factors into consideration, it is advisable to control it within the range of 0.90% to 1.10%.

[0017] Cr: Mainly used to improve the hardenability and tempering stability of steel, thereby improving the strength of steel. Usually, the Cr content in casing materials with excellent performance is mostly in the range of 1.0% to 1.2%. Due to the addition of a certain amount of Si and Ni, the amount of Cr added can be appropriately reduced to reduce costs while ensuring performance. Taking comprehensive considerations, it is advisable to control it in the range of 0.50% to 0.70%.

[0018] Mo: Mainly used to improve the hardenability and tempering stability of steel, thereby improving the strength and comprehensive mechanical properties of steel. Considering the influence of Mo / P on segregation and plasticity and toughness, it is advisable to control Mo / P≧25. Taking all factors into consideration, it is advisable to control it within the range of 0.30% to 0.50%.

[0019] Ni: Mainly used to improve the hardenability of steel, thereby improving the strength and low-temperature toughness of steel. Taking all factors into consideration, it is advisable to control it within the range of 0.30% to 0.50%.

[0020] V: added to steel to form VC and VN with C and N in steel, which has the effect of hindering the growth of austenite grains, refining grains, precipitation strengthening, and improving strength and plasticity and toughness. However, too high a content will form too many carbonitrides, which will increase the brittleness of the steel and increase the cost. Considering all factors, it is advisable to control it within the range of 0.05% to 0.10%.

[0021] Ti: It has the functions of deoxidation and nitrogen fixation when added to steel. It forms TiC and TiN with C and N in steel, which has the functions of hindering the growth of austenite grains and refining grains, thereby improving strength and toughness. However, too high a content will form too many carbonitrides, which will increase the brittleness of the steel and increase the cost. Taking all factors into consideration, it is advisable to control it within the range of 0.01% to 0.03%.

[0022] Re: It has the functions of deoxidation, desulfurization, reducing harmful gases, weakening the influence of harmful impurity elements, and modifying inclusions, and plays a role in purifying the molten steel. Considering all factors, it is advisable to control it within the range of 0 to 0.003%.

[0023] Ca: It can improve the properties and morphology of inclusions, thereby improving the toughness and corrosion resistance of steel. Considering the influence of Ca / S on plasticity and toughness, it is advisable to control Ca / S≧2. Taking all factors into consideration, it is advisable to control it within the range of 0.006% to 0.012%.

[0024] Al: It can form fine and evenly distributed oxides with oxygen, which can refine the grains and improve the strength and toughness. It is also an important deoxidizer. Considering the influence of Al / N on plasticity and toughness, it is advisable to control Al / N ≧ 2. Taking all factors into consideration, it is advisable to control it within the range of 0.010% to 0.015%.

[0025] P: Harmful impurity element, mainly affecting the plasticity and toughness of steel. It is advisable to control P ≤ 0.012%.

[0026] S: Harmful impurity element, mainly affecting the plasticity and toughness of steel. It is advisable to control S ≤ 0.003%.

[0027] N, H, O: harmful gas elements, mainly affecting the plasticity and toughness of steel. It is advisable to control N≤0.005%, N+H+O≤0.008%.

[0028] In a second aspect, a method for preparing the ultra-high strength petroleum casing described above comprises the steps of steelmaking, continuous casting, perforating, hot rolling and controlled rolling and controlled cooling, tempering heat treatment, hot straightening and hot warping, and thread processing.

[0029] Optionally, in the method for preparing the ultra-high strength petroleum casing, the steps of hot rolling, controlled rolling, controlled cooling and tempering specifically include:

[0030] The continuous casting billet is heated in a ring heating furnace at a temperature of 1185-1215°C and a holding time of 90-120 minutes, hot-pierced at 1165-1195°C, and hot-rolled at 910-1150°C, with the deformation of the hot rolling controlled to be ≥70%;

[0031] Control the final rolling temperature at 910-930℃, spray water quenching inside and outside, cooling rate ≥20℃ / s, temper at 640-660℃ for 60-90min, and water cool after tempering.

[0032] Optionally, in the preparation method of the ultra-high strength petroleum casing, in the tempering heat treatment step, the heating temperature is 890-910°C, the holding time is 60-90min, the inside and outside are water-sprayed for quenching, the cooling rate is ≥20°C / s, the temperature is tempered at 520-580°C for 90-120min, and the tempering is followed by water cooling.

[0033] Optionally, in the method for preparing the ultra-high strength petroleum casing, the heat straightening and heat sizing temperatures are 490°C to 550°C.

[0034] In the present invention, in terms of the tube blank preparation process, the material is mainly made to obtain a fine and uniform tempered sorbite microstructure through steelmaking (including refining outside the furnace, vacuum degassing), continuous casting, hot rolling and controlled rolling and cooling in the austenite zone, heat treatment, hot straightening and hot warping, etc., to achieve a reasonable match between the strength of the casing and good plastic toughness. For ultra-high steel grade casing, hot rolling and controlled rolling and controlled cooling processes can be used to improve the comprehensive mechanical properties of the casing.

[0035] The preparation process of the ultra-high strength casing comprises the following steps:

[0036] S1. Steelmaking: batching, oxygen-blown converter steelmaking, refining outside the furnace and vacuum degassing to obtain the above chemical composition, adding a small amount of rare earth alloy when necessary, feeding Si-Ca wire to control the deformation of inclusions in the steel.

[0037] S2. Continuous casting: The molten steel is cast into rod-shaped continuous casting billets. Electromagnetic stirring and light pressure reduction technology are used during the continuous casting process to control the segregation in the continuous casting billets.

[0038] S3. Piercing, hot rolling and controlled rolling: heat the continuous casting billet in a ring-shaped heating furnace with a heating furnace temperature of 1185-1215°C and a holding time of 90-120 min. perform hot piercing at 1165-1195°C and hot rolling at 910-1150°C. Control the hot rolling deformation to be ≥70%.

[0039] S4, heat treatment: control the final rolling temperature to 910-930℃, spray water quenching inside and outside, cooling rate ≥20℃ / s, tempering at 640-660℃ for 60-90min, and water cooling after tempering to avoid possible temper brittleness. Through the precise control of hot rolling deformation, rolling temperature (especially final rolling temperature), and cooling rate, a good strengthening and toughening effect is obtained; then, reheat to 890-910℃, keep warm for 60-90min, spray water quenching inside and outside, cooling rate ≥20℃ / s, tempering at 520-580℃ for 90-120min, and water cooling after tempering. Through heat treatment, a fine and uniform tempered troostite microstructure (grain size 9-10) is obtained to ensure the strength, plasticity and toughness of the casing.

[0040] S5. Hot straightening and hot sizing: After heat treatment, hot straightening and hot sizing are carried out. The hot straightening and hot sizing temperature is controlled at 490℃~550℃, and then water-cooled. Through hot straightening and hot sizing, the geometric dimensions of the steel pipe meet the requirements, and the residual stress of the casing is effectively controlled to improve the performance of the casing.

[0041] S6. Nondestructive testing and thread processing: Perform nondestructive testing on the casing body; then process API standard threads or special threads on the pipe end according to user requirements, and perform magnetic particle testing on the threads.

[0042] Beneficial effects: Compared with the prior art, the ultra-high strength casing material of the present invention has excellent comprehensive performance after appropriate preparation process, and the strength reaches the requirements of 150, 155, 160, 165, and 170 ksi steel grades respectively. It has a reasonable match of high strength, good plasticity and toughness, and has good economy, which can meet the needs of ultra-high strength casing for the efficient development of ultra-deep wells and extra-deep wells in complex working conditions. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the present invention more clear, the implementation methods of the present invention will be further described in detail below in conjunction with implementation cases.

[0044] Example

[0045] The chemical compositions of the ultra-high strength casing with yield strength levels of 150, 155, 160, 165, and 170 ksi provided by the embodiments of the present invention are shown in Table 1, wherein N≤0.005%, N+H+O≤0.008%, and the remainder is Fe and unavoidable impurities.

[0046] Table 1 Chemical composition of ultra-high strength casing of Example (mass percentage, %)

[0047] Edit number C S Mn P S Cr Mo Ni V Ti Re Al Ca 1(150) 0.24 0.49 0.93 0.012 0.002 0.52 0.33 0.30 0.07 0.02 - 0.010 0.007 2(150) 0.25 0.45 0.90 0.010 0.001 0.50 0.35 0.32 0.05 0.03 0.001 0.015 0.008 3(150) 0.23 0.47 0.92 0.011 0.002 0.54 0.30 0.34 0.06 0.01 0.001 0.013 0.006 4(155) 0.27 0.51 0.95 0.012 0.001 0.55 0.36 0.38 0.06 0.02 - 0.012 0.009 5(155) 0.26 0.55 0.96 0.010 0.002 0.58 0.39 0.36 0.08 0.02 0.001 0.013 0.011 6(155) 0.25 0.53 0.94 0.011 0.002 0.57 0.37 0.37 0.07 0.03 0.001 0.012 0.010 7(160) 0.27 0.57 0.98 0.010 0.001 0.62 0.41 0.40 0.07 0.03 - 0.010 0.013 8(160) 0.26 0.59 0.97 0.012 0.001 0.60 0.45 0.39 0.07 0.02 0.002 0.015 0.015 9(160) 0.28 0.56 1.00 0.009 0.002 0.65 0.43 0.43 0.08 0.02 0.002 0.011 0.012 10(165) 0.27 0.60 1.02 0.012 0.001 0.67 0.44 0.45 0.08 0.03 - 0.012 0.014 11(165) 0.29 0.58 1.06 0.010 0.001 0.66 0.42 0.44 0.07 0.02 0.002 0.014 0.013 12(165) 0.28 0.62 1.03 0.011 0.001 0.68 0.46 0.46 0.08 0.03 0.003 0.013 0.014 13(170) 0.28 0.65 1.08 0.009 0.001 0.70 0.47 0.49 0.09 0.03 - 0.014 0.012 14(170) 0.30 0.61 1.05 0.010 0.001 0.64 0.48 0.50 0.10 0.02 0.003 0.015 0.011 15(170) 0.29 0.63 1.10 0.009 0.001 0.67 0.50 0.48 0.09 0.03 0.003 0.013 0.013

[0048] The embodiment of the present invention also provides a method for preparing an ultra-high strength casing with a yield strength level of 150, 155, 160, 165, 170 ksi, comprising the following steps:

[0049] Steelmaking: batching, oxygen-blown converter steelmaking, after refining outside the furnace and vacuum degassing, the chemical composition in Table 1 is obtained. A small amount of rare earth alloy can be added, and Si-Ca wire can be fed to control the deformation of inclusions in the steel.

[0050] Continuous casting: The molten steel is cast into rod-shaped continuous casting billets. During the continuous casting process, electromagnetic stirring and soft pressure reduction technology are used to control the segregation in the continuous casting billets.

[0051] Hot rolling, controlled rolling, controlled cooling and tempering: heat the continuous casting billet in a ring heating furnace, the heating furnace temperature is 1200±15℃, the holding time is 120min, hot piercing is performed at 1165~1195℃, the initial rolling temperature is 1140±10℃℃, the final rolling temperature is 920±10℃, the hot rolling deformation is controlled to be ≥70%, internal and external water spray cooling, the cooling rate is ≥20℃ / s. Then temper at 650±10℃ for 60min, and water cooling is performed after tempering.

[0052] Quenching and tempering heat treatment, hot straightening and hot sizing: According to the different performance requirements of different steel grade casing, different quenching and tempering heat treatment and subsequent hot straightening and hot sizing process parameters are adopted (see Table 2). Reheating temperature 900±10℃, heat preservation 60~90min, internal and external water spray quenching, cooling rate ≥20℃ / s, (530~570)±10℃ tempering 90~120min, water cooling after tempering; metallographic structure is tempered troostite, grain size 9~10. Hot straightening and sizing temperature (500~540)±10℃, then water cooling.

[0053] Nondestructive testing and thread processing: Perform nondestructive testing on the tubing and casing bodies; then process API standard threads or special threads on the pipe ends according to user requirements, and perform magnetic particle testing on the threads.

[0054] Performance characteristics: The ultra-high strength casing material of the present invention has excellent comprehensive performance (see Table 2 for details) and good economic efficiency after undergoing appropriate preparation technology.

[0055] Table 2 Preparation process and performance of ultra-high strength casing in Example

[0056]

[0057]

[0058] Among them, the yield strength of 150ksi steel grade casing is 1099~1110MPa, the tensile strength is 1195~1207MPa, the elongation is 22%, the 0℃ transverse Charpy V-notch impact toughness is 121~126J, and the cold brittle transition temperature FATT50 is -60℃; the yield strength of 155ksi steel grade casing is 1136~1145MPa, the tensile strength is 1235~1245MPa, the elongation is 21%, the 0℃ transverse Charpy V-notch impact toughness is 113~118J, and the cold brittle transition temperature FATT50 is -55℃; the yield strength of 160ksi steel grade casing is 1169~1181MPa, the tensile strength is 1271~1284MPa , elongation 20%, 0℃ transverse Charpy V-notch impact toughness 101~108J, cold brittle transition temperature FATT50 is -50℃; 165ksi steel grade casing yield strength 1202~1213MPa, tensile strength 1307~1318MPa, elongation 19%, 0℃ transverse Charpy V-notch impact toughness 92~98J, cold brittle transition temperature FATT50 is -45℃; 170ksi steel grade casing yield strength 1237~1248MPa, tensile strength 1345~1357MPa, elongation 18%, 0℃ transverse Charpy V-notch impact toughness 82~88J, cold brittle transition temperature FATT50 is -40℃. It can meet the needs of ultra-high strength casing for the efficient development of ultra-deep wells and ultra-deep wells in complex working conditions.

[0059] Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultra-high strength petroleum casing, characterized in that: The chemical composition of the casing is as follows by mass percentage: C: 0.23%-0.30%, Si: 0.45%-0.65%, Mn: 0.90%-1.10%, P≤0.012%, S≤0.003%, Cr: 0.50%-0.70%, Mo: 0.30%-0.50%, Ni: 0.30%-0.50%, V: 0.05%-0.10%, Ti: 0.01%-0.03%, Re: 0-0.003%, Al: 0.010%-0.015%, Ca: 0.006%-0.010%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities; The method for preparing the ultra-high strength petroleum casing comprises the steps of: steelmaking, continuous casting, perforating, hot continuous rolling and controlled rolling and controlled cooling, quenching and tempering heat treatment, hot straightening and hot warping, and thread processing; The steps of hot rolling, controlled rolling, controlled cooling and tempering specifically include: The continuous casting billet is heated in a ring heating furnace at a temperature of 1185-1215°C and a holding time of 90-120 minutes. The billet is hot-pierced at 1165-1195°C and hot-rolled at 910-1150°C. The deformation of hot rolling is controlled to be ≥70%. Control the final rolling temperature at 910-930℃, spray water quenching inside and outside, cooling rate ≥20℃ / s, temper at 640-660℃ for 60-90min, and water cool after tempering.

2. The ultra-high strength petroleum casing according to claim 1, characterized in that: The chemical composition of the casing is as follows by mass percentage: C: 0.23%-0.24%, Si: 0.45%-0.49%, Mn: 0.90%-0.93%, P: 0.010%-012%, S: 0.001%-0.002%, Cr: 0.50%-0.54%, Mo: 0.30%-0.35%, Ni: 0.30%-0.34%, V: 0.05%-0.07%, Ti: 0.01%-0.03%, Re: 0-0.001%, Al: 0.010%-0.015%, Ca: 0.006%-0.008%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

3. The ultra-high strength petroleum casing according to claim 1, characterized in that: The chemical composition of the casing is as follows by mass percentage: C: 0.25%-0.27%, Si: 0.51%-0.55%, Mn: 0.94%-0.96%, P: 0.010%-012%, S: 0.001%-0.002%, Cr: 0.55%-0.58%, Mo: 0.36%-0.39%, Ni: 0.36%-0.38%, V: 0.06%-0.08%, Ti: 0.02%-0.03%, Re: 0-0.001%, Al: 0.012%-0.013%, Ca: 0.009%-0.011%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

4. The ultra-high strength petroleum casing according to claim 1, characterized in that: The chemical composition of the casing is as follows by mass percentage: C: 0.26%-0.28%, Si: 0.56%-0.59%, Mn: 0.97%-1.00%, P: 0.009%-012%, S: 0.001%-0.002%, Cr: 0.60%-0.65%, Mo: 0.41%-0.45%, Ni: 0.39%-0.43%, V: 0.07%-0.08%, Ti: 0.02%-0.03%, Re: 0-0.002%, Al: 0.010%-0.015%, Ca: 0.012%-0.015%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

5. The ultra-high strength petroleum casing according to claim 1, characterized in that: The chemical composition of the casing is as follows by mass percentage: C: 0.27%-0.29%, Si: 0.58%-0.60%, Mn: 1.02%-1.03%, P: 0.010%-012%, S: 0.001%, Cr: 0.66%-0.68%, Mo: 0.42%-0.46%, Ni: 0.44%-0.46%, V: 0.07%-0.08%, Ti: 0.02%-0.03%, Re: 0-0.003%, Al: 0.012%-0.014%, Ca: 0.013%-0.014%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

6. The ultra-high strength petroleum casing according to claim 1, characterized in that: The chemical composition of the casing is as follows by mass percentage: C: 0.28%-0.30%, Si: 0.61%-0.65%, Mn: 1.05%-1.10%, P: 0.009%-010%, S: 0.001%, Cr: 0.64%-0.70%, Mo: 0.47%-0.50%, Ni: 0.48%-0.50%, V: 0.09%-0.10%, Ti: 0.02%-0.03%, Re: 0-0.003%, Al: 0.013%-0.014%, Ca: 0.011%-0.014%, N≤0.005%, N+H+O≤0.008%, and the balance is Fe and unavoidable impurities.

7. The ultra-high strength petroleum casing according to claim 1, characterized in that: In the tempering heat treatment step, the heating temperature is 890-910°C, the holding time is 60-90min, the internal and external water spray quenching, the cooling rate is ≥20°C / s, the tempering is 520-580°C for 90-120min, and the tempering is followed by water cooling.

8. The ultra-high strength petroleum casing according to claim 1, characterized in that: The hot straightening and hot sizing temperatures are 490°C to 550°C.

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